*What is a Regular Expression?*

A regular expression (RegEx) is a sequence of characters that forms a search pattern. It’s commonly used for:

- Email and phone number validation
- Searching for patterns in text
- Data cleaning and extraction

*Python’s re Module – Basics*

import re

*1. re.search() –* Looks for a match anywhere in the string

text = My email is hello@example.com
match = re.search(rw+@w+.w+, text)

if match:
print(Found:, match.group())

Output: Found: hello@example.com


*2. re.findall() –* Returns all matches as a list

text = Emails: one@mail.com and two@site.org
emails = re.findall(rw+@w+.w+, text)
print(emails)

Output: ['one@mail.com', 'two@site.org']


*3. re.sub() – Replaces all matches*

text = Hello 123, this is test 456
cleaned = re.sub(rd+, *, text)
print(cleaned)

Output: Hello *, this is test *

*Common Patterns*

- PatternDescription

dAny digit (0-9)
wAny alphanumeric character
sAny whitespace (space/tab)
.Any character (except newline)
+One or more repetitions
*Zero or more repetitions
Start of string
End of string


*Mini Task: Extract Phone Numbers*

text = Call me at 9876543210 or 9123456789
numbers = re.findall(rd10, text)
print(Phone numbers found:, numbers)

Output: ['9876543210', '9123456789']


*What You Practiced* :

- Writing and using regular expressions
- Using re.search(), re.findall(), and re.sub()
- Cleaning and extracting patterns from text
- Real-world data handling